Femto base stations, or home base stations, have attracted much attention in the wireless industry. In the Universal Terrestrial Radio Access Network (UTRAN) and the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), the features associated with the femto base station such as mobility and interference management have been introduced. The femto base stations are already operational in 2G and 3G communication systems such as the Global System for Mobile communication (GSM) system and the 3GPP2 Code Division Multiple Access 2000 (CDMA 2000) system.
Access to a home base station or a group of home base stations may be under the control of the operator or the owner of the home base station, who decides whether a given user may or may not connect to that home base station. Only the subscribers to the group of the home base station are allowed to connect to the home base station, known as a closed subscriber group (CSG). In the CSG, mobility management is employed to prevent a handover of a CSG subscriber to a neighboring home base station that does not belong to the same CSG. Therefore, before initiating a handover to a target cell, the serving home base station is required to identify whether a target home base station which serves the target cell belongs to the same CSG.
In order to determine the identity and type of potential target cells, the serving home base station can instruct the CSG subscriber to collect the system information of all potential target cells and conduct a measurement regarding the potential target cells. In response to the request, the CSG subscriber can acquire system information and measurements from the potential target base stations, and return a report including the acquired information to the serving home base station. Specifically, the CSG subscriber can report a unique identifier of the target cell, known as a Cell Global Identifier (CGI), to the serving home base station. Further, the report also includes information on how well a signal from the target cell is received, based on which the serving home base station can determine whether to initiate a handover to the target cell.
The CSG subscriber can collect the system information and the measurements during a discontinuous reception (DRX) gap or an autonomous gap, of which the DRX gap is defined by the network and the autonomous gap is initiated by the CSG subscriber. The conditions for using the DRX gap and the autonomous gap to collect the system information and the cell measurements have not been established.